I. Field of the Invention
The present invention relates generally to transponder-responder systems and, more particularly, to such a system in which a remote station generates an emergency distress signal in response to an interrogation signal from a home station. The home station receives the emergency distress signal and includes circuitry which not only determines the location of the remote station but also decodes the distress signal to thereby determine the type of emergency in accordance with a preset code.
II. Description of the Prior Art
The sport or hobby of boating, both power and sail, has enjoyed increased popularity in recent years. Due to the increase in cost with the increase in size of such boats, many if not most of such boats in use today are relatively small in size.
These small crafts, however, lack both the navigational and structural sophistication of large vessels. As a result, these small crafts oftentimes go astray of their intended course and become grounded, strike reefs, and the like.
Moreover, small boats are particularly susceptible to other emergency situations. For example, such boats frequently run out of gas or suffer engine damage or failure such that the boat cannot return to shore. Still more serious emergency situations can arise in small boats during bad weather conditions when some boats can even be capsized.
Heretofore, small boats endangered by one emergency situation or another have relied primarily on a visual sighting and the aid of rescuers to provide the needed help. The visual sighting of a boat in distress, of course, can be accomplished from another boat, airplane, helicopter or the like.
The visual sighting of a boat in distress, however, is hampered by weather conditions such as fog and rain and also by nightfall. In fact, when the approximate location of a missing ship is unknown, a night search in an attempt to locate the missing ship is virtually useless. As a result of all of these factors, the ultimate sighting of a ship in distress oftentimes is too late to aid its occupants.
In order to minimize the above-mentioned dangers, many ships now have radio telephones installed in them. Such radio telephones, while expensive to obtain, are effective in signaling for help when the captain of the ship knows his location in the water. However, in many situations and particularly in bad weather, the ship is diverted from the course and the captain is unaware of his location. In this event, the position of the ship can still be identified by triangulation. Triangulation, however, is not precise so that only the approximate location of the ship can be determined. Moreover, triangulation is expensive since it requires at least two and preferably three spaced receivers at predetermined locations, typically along the shoreline. Consequently, the triangulation method to locate the position of a ship in distress is not widely used except in extreme emergencies.